Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C7/00—Purification; Separation; Use of additives
  • C07C7/20—Use of additives, e.g. for stabilisation

Definitions

• the present invention relates to the stabilization of ethylenically unsaturated compounds, more particularly, to the inhibition of undesired polymerization of vinylaromatic compounds during storage, shipping or processing. Specifically, this invention relates to the use of zinc or nickel salts of dialkyl-dithiocarbamates as a polymerization inhibitor for the processing of dialkenylbenzene.
• the problem of undesired polymerization of monomer is particularly acute during purification operations.
• Spontaneous polymerization is disadvantageous because it causes fouling of distillation column reboilers and other equipment used for processing vinylaromatic monomers.
• spontaneous polymerization is an economic burden that results in loss of monomer and a decrease in overall process efficiency.
• U.S. Patent No. 4,409,480 is concerned with the use of compounds such as N-dialkylhydroxylamines and tertiary alkylcatechols and their synergistic effect as a stabilization system for vinylaromatic compounds.
• U.S. Patent No. 4,389,285 discloses an improved method for preparing and processing ethylenically unsaturated aromatic monomers, in that 3,5-dinitrosalicylic acid as used as a process inhibitor.
• Vinylaromatic monomers such as styrene, alpha-alkylstyrene, vinyltoluene, divinylbenzene, meta- and para- diisopropenylbenzene are important for their ability to form useful polymeric materials. These compounds are typically prepared by catalytic dehydrogenation of alkylaromatic compounds having corresponding carbon chains. The crude product of the dehydrogenation reaction, however, is a mixture of materials comprising in addition to the desired vinyl or divinylaromatic monomer various alkylaromatic compounds. These other substances must be separated from the monomer to obtain a commercially useful product.
• dithiocarbamates more specifically, zinc or nickel dialkyldithiocarbamates provide outstanding polymerization inhibiting activity for vinylaromatic monomers, more specifically, dialkenylbenzenes.
• zinc or nickel dialkyldithiocarbamate it is now possible to provide superior polymerization inhibiting protection over those materials presently accepted in the industry.
• the present invention provides stable compositions of vinylaromatic monomers and a method for effectively and economically inhibiting spontaneous polymerization of styrene, vinylaromatic monomers and, more specifically, meta- and para- diisopropenylbenzenes.
• the present invention relates to the use of zinc or nickel dialkyldithiocarbamates, more specifically, zinc dialkyldithiocarbamates as polymerization inhibitors in the preparation of readily polymerizable ethylenically unsaturated aromatic compounds.
• process inhibitor refers to a polymerization inhibitor which is employed during the preparation and processing of the monomer.
• the present invention is applicable to readily polymerizable ethylenically unsaturated aromatic compounds.
• Such compounds include: meta- and para- diisopropenylbenzene, styrene, a-methylstyrene, vinyltoluene, vinylnapthalene, divinylbenzene, etc.
• Compounds preferred for use in the process of the present invention include diisopropenylbenzene and a-methylstyrene with diisopropenylbenzene being particularly preferred.
• the crude monomer is typically subjected to vacuum distillation in order to remove excess reactants and other volatile aromatic impurities.
• zinc or nickel dialkyldithiocarbamates are employed as a process inhibitor during the preparation of the monomer and especially during the distillation step, which is when polymerization is most likely to occur.
• the zinc or nickel dialkyldithiocarbamates can be supplied to the process in a variety of ways.
• the dithiocarbamate is normally mixed with the crude reactor effluent before distillation. In this manner the reaction product is protected throughout the entire distillation process.
• the zinc or nickel dialkyldithiocarbamates are provided to the reaction system in an amount which is sufficient to effect the inhibition of polymerization.
• the zinc or nickel dialkyldithiocarbamate will be present in an amount of about 10 to 3000 ppm (parts per million) based upon the weight of reactants and products present in the distillation column.
• the dithiocarbamate is present in a concentration of from 250 to 2000 ppm with a concentration of from 500 to 1000 ppm being especially preferred.
• the dithiocarbamates can be provided to the diisopropenylbenzene preparation process either directly or as a stock solution.
• Zinc dialkyldithiocarbamate is sufficiently soluble in a suitable carrier solvents to allow the preparation of such a stock solution.
• suitable carrier solvents are the chlorinated hydrocarbons, such as chloroform.
• Additional inhibitors may also be present during the process of the present invention.
• product inhibitors such as t-butylcatechol may also be present during the preparation and/or distillation of the crude monomer.
• the zinc or nickel dialkyldithiocarbamates can be made by the reaction of secondary amines with carbon disulfide in the presence of a metal hydroxide according to the following reaction: wherein R + R can be the same or different radical of 1 to 10-carbon atoms and M is zinc or nickel.
• R + R can be the same or different radical of 1 to 10-carbon atoms and M is zinc or nickel.
• zinc dibutyldithiocarbamate shows a marked improvement over all inhibitors for the stabilization of p-diisopropenylbenzene and is also effective for the meta isomer.
• the process of the instant invention provides an inhibitor wherein diisopropenylbenzene losses are minimized and purification is made much easier.
• the use of zinc dibutyldithiocarbamate has been successful in the distillation of para- diisopropenylbenzene on a pilot plant scale, thus indicating potential commercial success.
• the inhibitor can be formulated to contain more than one member from the specified class of compounds.

Landscapes

• Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Analytical Chemistry (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Water Supply & Treatment (AREA)
• Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)

Applications Claiming Priority (2)

Publications (3)

Family

ID=24343017

Family Applications (1)

Country Status (5)

Cited By (3)

Families Citing this family (2)

Citations (2)

Family Cites Families (12)

• 1984
  • 1984-03-02 US US06/585,801 patent/US4532011A/en not_active Expired - Lifetime
• 1985
  • 1985-02-05 CA CA000473572A patent/CA1224218A/fr not_active Expired
  • 1985-02-26 DE DE8585630020T patent/DE3563612D1/de not_active Expired
  • 1985-02-26 EP EP85630020A patent/EP0155898B1/fr not_active Expired
  • 1985-03-01 JP JP60040958A patent/JPH0665653B2/ja not_active Expired - Lifetime

Patent Citations (2)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events